Patients with Hurler’s disease often have a poor prognosis. Most patients will face life-threatening conditions at a young age. New treatment strategies have been developed, including enzyme replacement therapy and bone marrow transplants. Each of these treatment strategies attempts to re-introduce lysosomal alpha-L-iduronidase to the body. These treatments have significantly improved the lifespan of patients with Hurler’s disease, however they do not halt the progression of the orthopedic deformities often present in those with Hurler’s. Therefore, orthopedic deformity correction becomes a crucial aspect of treatment of Hurler’s disease, in order to restore function and improve quality of life for these patients.
The orthopedic difficulties characteristic of Hurler’s disease are thought to arise from a lack of ossification in major joints. Ossification is the process where cartilage is converted to bone. Patients with Hurler’s disease have large amounts of sugar molecules in their joint fluid. This is thought to interfere with ossification and bone remodeling, although the exact mechanism is not understood.
At the Paley Institute we address the orthopedic difficulties of Hurler’s disease. We correct the limb deformities of the hips, knees, and hands with reconstructive surgery.
One of the primary sites of ossification failure in patients with Hurler’s disease is at the acetabulum of the hip joint. This results in hip dysplasia and dislocation. An arthrogram of the hip can be used to quantify the degree of ossification of the acetabulum and the femoral head.
In order to correct the hip dysplasia, Dr. Paley can perform a hip containment surgery. The goal of the surgery is to increase the surface area interaction between the hip and the femoral head in order to correct the dysplasia and prevent further dislocation. Containment surgery increases femoral head coverage by reorienting the femur and / or the acetabulum using specialized osteotomies (surgical bone cuts). Osteotomies of the hip, femur, or both can be performed.
For more information, see Containment Treatment under Perthes Disease.
Failure of ossification in the knee joint can result in progressive genu valgum of the knees (knock knees). Genu valgum of the knees typically develops between the ages of 2 and 5. Surgical reconstruction is typically required since the deformity will not correct on its own as the patient ages.
Dr. Paley will correct the genu valgum using a process called hemiepiphysiodesis. A small metal plate (called an 8-plate) is stapled to one side of the growth plate at the knee. This will cause growth on only one side, gradually straightening out the knee joint. This is a slow, gradual process that occurs as the patient ages. If the patient is at skeletal maturity, a hemiepiphysiodesis cannot be performed.
In addition to hemiepiphysiodesis, Dr. Paley can correct the genu valgum with a specialized intra-articular osteotomy called a tibial plateau elevation. This is an acute correction. During surgery Dr. Paley will apply internal fixation to hold the alignment in place.
Many patients with Hurler’s disease present with carpal tunnel syndrome. This tends to worsen as the patient ages. Dr. Paley can perform a surgical release of the carpal tunnel. A tenosynevectomy (excision of the tendon) of the flexor retinaculum may also be performed.